The present invention relates to an imaging unit for endoscopes capable of being autoclaved with an imaging device incorporated therein while being mounted in an endoscope.
Recently, when an optical endoscope is used to optically propagate an optical image to a proximal part thereof by way of relay lenses or the like, an imaging unit for endoscopes is generally adopted to pick up the optical image so as to convert it into an electric signal. This is intended to display the optical image formed by the endoscope on a monitor or to store the optical image in an image recording apparatus.
This type of imaging unit for endoscopes comprises a focusing lens and an imaging device such as a charge-coupled device (CCD). The focusing lens has an optical image, which is propagated from an eyepiece unit in an endoscope, converged thereon. The imaging device picks up the optical image converged on the focusing lens. For successfully successfully picking up an optical image, the focusing lens and imaging device must be aligned with each other. For accomplishing the alignment, the imaging device and focusing lens must be aligned with each other in optical-axis directions and in directions of eccentricity (focusing mechanism), that is, directions perpendicular to the optical axis (eccentricity adjusting mechanism). The alignment in the optical-axis directions is achieved by optimizing a distance between the imaging device and focusing lens.
For example, Japanese Unexamined Patent Publication No. 2-87110 has proposed an imaging unit that includes as separate apparatuses a camera adaptor in which an image formation optical system is incorporated and a camera head in which an imaging device is incorporated. A focusing mechanism and an eccentricity adjusting mechanism are included for adjusting the positions of various optical systems.
In recent years, what is referred to as autoclaving has been adopted as an inexpensive sterilizing method for sterilizing an imaging unit for endoscopes. According to the autoclaving method, an object of sterilization.is left intact within high-pressure steam for a certain period of time. When it says that an imaging unit for endoscopes resists autoclaving, the imaging unit must have a focusing lens and an imaging device sealed hermetically.
However, the imaging unit for endoscopes described in the Japanese Unexamined Patent Publication No. 2-87110 must include the focusing adjusting mechanism and eccentricity adjusting mechanism. It is therefore hard to hermetically seal the movable components included in an adjusting mechanism while keeping the imaging unit resistive to autoclaving.
For example, Japanese Unexamined Patent Publication No. 10-258034 has proposed an imaging unit for endoscopes in which a focusing method that enables autoclaving is implemented and a means for driving a motor-driven aperture stop unit is incorporated.
However, the imaging unit for endoscopes described in the Japanese Unexamined Patent Publication No. 10-258034 must have an adaptor and a camera head detached from each other before being autoclaved. After the autoclaving is completed, when the imaging unit for endoscopes is reused, the adaptor and camera head must be attached to each other again. This is annoying. If this procedure is ignored, steam remaining in the adaptor and camera head may condense to blur an optical image.
Moreover, an aperture stop unit helpful in improving a depth of focus, which permits an optical image propagated from an eyepiece unit 13 in an endoscope that offers a small depth of focus to be observed clearly, includes a rotational driving structure. In efforts to reduce the size of the aperture stop unit, a focusing lens is incorporated in the rotational driving structure. Therefore, when the focusing lens must be movable, the aperture stop unit must be made larger in size or the diameter (effective diameter) of the lens must be made smaller. Otherwise, a mechanism for moving the focusing lens along the optical axis of an optical system including the focusing lens must be included in the aperture stop unit. Otherwise, the camera head must be made larger in size in order to interpose another focusing lens between the aperture stop unit and imaging device. In this case, if an engagement length along the optical axis of the camera head is set to a length required for suppressing the tilt of the focusing lens, the camera head becomes very large. This poses a problem. Furthermore, since a hermetic connector is required in order to mount the aperture stop unit, the camera head becomes structurally complex, large in size, and costly.
In contrast, Japanese Unexamined Patent Publication No. 10-179505 has proposed an imaging unit for endoscopes in which a lens and an imaging device are integrated with each other. Herein, magnets are used to drive the lens for focusing.
However, the imaging unit for endoscopes described in the Japanese Unexamined Patent Publication No. 10-179505 cannot adjust eccentricity after a hermetic seal member is constructed. Moreover, magnetic coupling force has limitations (for increasing the force, it is necessary to extend the distance between the north and south poles of each of paired magnets or to increase the number of pairs of magnets). When measures are taken in order to intensify the magnetic coupling force, frictional resistance occurring on a sliding surface increases. This necessitates a clearance between a lens barrel and a locking frame. The clearance results in a displacement of a view image. A known countermeasure is employment of an elastic member. However, the magnetic coupling force must be further intensified in order to cancel constraining force exerted by the elastic member. Consequently, eccentricity of an optical image cannot be suppressed any longer.
In the imaging unit for endoscopes described in the Japanese Unexamined Patent Publication No. 10-258034, the adaptor and camera head are detached from each other before autoclaving. After the autoclaving is completed, when the imaging unit for endoscopes is reused, the adaptor and camera head must be attached to each other. This handling annoys a user. Moreover, the aperture stop unit includes the rotational driving structure in which the focusing lens is incorporated for the purpose of realizing a compact design. Therefore, when the lens must be movable, a mechanism for moving the lens along the optical axis must be included in the aperture stop unit. Otherwise, the camera head must be made larger in size in order to interpose another focusing lens between the aperture stop unit and imaging device. In this case, if an engagement length along the optical axis of the camera head is set to a length suppressing the tilt of the lens, the camera head must be made very large. Besides, a hermetic connector is required in order to mount the aperture stop unit. Therefore, the imaging unit becomes structurally complex, large in size, and costly.
On the other hand, in the imaging unit for endoscopes described in the Japanese Unexamined Patent Publication No. 10-179505, after the hermetic seal member is constructed, eccentricity cannot be adjusted. Moreover, the magnetic coupling force has limitations. When measures are taken to intensity the force, frictional resistance occurring on a sliding surface increases. Consequently, a clearance must be preserved between the lens barrel and locking frame. The clearance results in a displacement of a view image. When an elastic member is included as a countermeasure, the magnetic coupling force must be further intensified in order to cancel constraining force exerted by the elastic member. Consequently, eccentricity of an optical image cannot be suppressed.
The present invention attempts to break through the foregoing situation. An object of the present invention is to provide an imaging unit for endoscopes capable of being autoclaved without the necessity of dismounting optical elements and an imaging device. Moreover, the imaging unit for endoscopes offers excellent maneuverability. Furthermore, the position of the imaging device relative to the optical elements can be adjusted with the imaging unit kept hermetic.
In an optical system adjusting mechanism included in a conventional imaging unit for endoscopes which has been disclosed in, for example, Japanese Examined Patent Publication No. 4-58753, a turning pair that can be turned with the imaging surface of an imaging device as a center of rotation is realized using a frame. The position of the imaging device along the optical axis of an optical system including the imaging unit is adjustable.
According to Japanese Unexamined Patent Publication No. 2-289225, a turning pair is included, and a lens barrel is made movable arbitrarily along the optical axis of an optical system.
According to Japanese Examined Patent Publication NO. 4-58753, a mechanism for adjusting a swing (eccentricity) of an imaging device and adjusting the position of the imaging device relative to an optical system includes a turning pair whose center is aligned with the center of the imaging surface of the imaging device. The mechanism is effective in adjusting the swing. The imaging device and a frame that holds the imaging device can be moved in optical-axis directions.
According to Japanese Unexamined Patent Publication No. 2289225, a unit cylinder that bears an imaging device includes a turning pair and enables adjustment of a swing. Although an operator can finely adjust an optical system, the operator is not permitted to arbitrarily adjust the imaging device itself Furthermore, it is impossible to prevent invasion of high-pressure steam generated during autoclaving.
For example, Japanese Unexamnined Patent Publication No. 10-179505 has disclosed an art that a lens and an imaging device are integrated with each other and stowed in a hermetic frame. The lens is driven externally using magnets, whereby focusing is achieved. According to the related art, since the lens and imaging device are stowed in the hermetic frame, even when autoclaving is performed, high-pressure steam will not invade into the hermetic frame.
For accomplishing the above object, a first imaging unit for endoscopes in accordance with the present invention consists mainly of optical elements, an imaging device, a hermetic seal member, and an imaging device driving means. The optical elements form an optical image. The imaging device photoelectrically converts the optical image. The hermetic seal member has at least the optical element and the imaging device incorporated therein. The imaging device driving means makes it possible to arbitrarily adjust the position of the imaging device relative to the optical elements from outside the hermetic seal member.
A second imaging unit for endoscopes is identical to the first imaging unit for endoscopes except that the imaging device driving means is an eccentricity adjusting means for adjusting eccentricity of the imaging device relative to the optical axis of the optical elements.
A third imaging unit for endoscopes is identical to the first imaging unit for endoscopes except that the imaging device driving means is a focusing means that moves the optical elements and imaging device along the optical axis.
A fourth imaging unit for endoscopes is identical to the third imaging unit for endoscopes except that the image plane of the imaging device is located substantially in the middle of an engagement length of a frame, which holds the imaging device, along the optical axis.
A fifth imaging unit for endoscopes is identical to the first imaging unit for endoscopes except that the imaging device driving means is an adjusting means that rotates the imaging device with the optical axis of the optical elements as a center.
Consequently, at least the optical elements and the imaging device are stowed in the hermetic seal member. The eccentricity of the imaging device relative to the optical elements is adjusted from outside the hermetic seal member, and focusing is performed from outside the hermetic seal member. The imaging unit can therefore be autoclaved without the necessity of dismounting the optical elements and imaging device. Moreover, the position of the imaging device relative to the optical elements can be adjusted with the imaging unit kept hermetic.